It is estimated that 100 million men and women are affected by urinary incontinence (UI). The prevalence of UI is generally higher in women than in men, women being between two (older age groups) and four times (younger and middle-aged) more likely to be incontinent than men. Hormone replacement has been the mainstay of medical therapy for women with urinary incontinence for several decades. However, two recently published long-term studies involving thousands of women showed that estrogen/progesterone therapy increased the incontinence rate. We have developed a rat model of stress urinary incontinence (SUI) and have since been actively involved in the study of female SUI. To investigate the hormonal effect on urinary incontinence, we treated our rat SUI models with placebo versus estrogen pellet. Consistent with the results of human studies mentioned above, our pilot study showed that estrogen treatment increased the rate of SUI. We went on to study the possible mechanism of this phenomenon and found that estrogen has differential effects on the vagina and urethra. We hypothesize that the relaxant effect of estrogen on the urethra contributes to the increase incontinence rate particularly in those women who already have "compromised" continence mechanism. We also hypothesize that better treatment options can be identified by studying the effect of selective estrogen receptor modulators (SERMs) as well as several known trophic factors for muscle and nerve. The hypotheses will be tested by completing the following specific aims. Our long term goal is to find better preventive and therapeutic measures for women with urinary incontinence. Specific Aim 1. To identify the effect of sex hormones and SERMs on female urinary continence. This will be accomplished by treating our established incontinence rat model with estrogen, progesterone, raloxifene, levormeloxifene, and growth hormone, followed by cystometrical analysis. Specific Aim 2. To elucidate the molecular mechanism associated with estrogen/progesterone induced incontinence. This will be accomplished by examining the urethra, bladder, vagina, and pelvic floor muscles for possible changes in myosin light chain phosphorylation, rho kinase expression, and VEGF promoter activity. Specific Aim 3. To identify better preventive and therapeutic options for stress urinary incontinence. This will be accomplished first by establishing primary urethra smooth muscle cell cultures and paracervical ganglion neurons from various groups of rats as in Specific Aim 1. The cell and ganglial cultures will be treated with estradiol, raloxifene, testosterone, and various growth factors, and analyzed for cell proliferation and neurite growth. Specific Aim 4. To identify the molecular mechanism through which estrogen modulates the expression of a1A adrenoceptor. This will be accomplished by analyzing various promoter constructs of the rat a1A adrenoceptor gene in the presence of estrogen and SERMs.